Dennis-Lane, 24, was swapped to the Saints for their on-traded round three selection, pick 47 overall.
The speedy goal-shark will reunite with his former WAFL coach Scott Watters at the Saints, after previously playing under him at Subiaco.
Dennis-Lane played 19 games for the Swans since being taken at pick 55 in the 2009 national draft.
He was starved of opportunity in 2012 to get a game for the powerhouse Swans, with the likes of Ben McGlynn and Lewis Jetta playing starring roles in Sydney’s premiership season.
Dennis-Lane will join Saints forward line veteran Stephen Milne as a fiery goalsneak option, alongside fellow youngsters Ahmed Saad and Terry Milera.